WiMAX is a broadband wireless access technology based on standards of IEEE (Institute of Electrical and Electronics Engineers) 802.16, which can effectively utilize limited wireless spectrum resources to provide a relatively wide air-interface bandwidth (with the maximum data transmission capacity of 70 Mbps). As shown in FIG. 1, the network reference model of WiMAX is made up of three logic entities: a mobile station/stationary station (MS/SS), an access service network (ASN) and a connection service network (CSN), wherein each of them represents a group of functional entities, and each functional entity may be implemented in a single physical device or in multiple physical devices. ASN mainly provides WiMAX subscribers with corresponding wireless access and control. CSN provides MS with IP connection service. When the subscriber roams, CSN is divided into a visited CSN (V-CSN) and a home CSN (H-CSN). In FIG. 1, R1 is a reference point between MS and ASN, R2 is a logic reference point, and R3 is a reference point between ASN and CSN. Dotted lines represent control signaling.
A home network service provider (Home NSP, H-NSP for short) is a local network service provider. H-NSP, being an operator or a business group, has service level agreement associated with WiMAX subscribers, authenticates and authorizes sessions of subscribers (within network or in roaming scenarios), and charging subscribers' service (charging and providing bills). For the purpose of supporting roaming service, a H-NSP may have roaming agreements with other NSP. A H-NSP network is made up of H-CSN (home connection service network), mainly including a home authentication, authorization and accounting server storing subscriber's subscription service and home agent (HA) network elements.
A visited network service provider (Visited NSP, V-NSP for short) is defined in the view of roaming subscribers, and roaming subscribers use the wireless coverage of V-NSP to access WiMAX service. V-NSP may have a roaming protocol with H-NSP of subscribers, and provides H-AAA service routing to H-NSP. Based on the WiMAX service request of subscribers and the protocol between H-NSP and V-NSP, V-NSP can provide roaming subscribers with some or all of the WiMAX services, or provide H-NSP with data/control service routing. V-NSP network mainly comprises a visited authentication, authorization and accounting server (V-AAA), which provides proxy forwarding function, and home agent (HA) network elements.
A network access provider (NAP) is a business unit providing WiMAX wireless access architecture for one or more WiMAX NSPs. NAP includes one or more ASNs, mainly comprising base station (BS) and access gateway (ASN-GW).
Foreign agent (FA) is a functional entity in ASN-GW, providing the foreign agent function for a mobile IP terminal.
Home agent (HA) is a function entity of CSN, providing home agent function for the mobile IP terminal. HA may be located in H-CSN, or in V-CSN.
WiMAX network needs to adopt mobile IP as a mobility management protocol. In mobile IP framework, mobile IP client maintains fixed home network IP address among different FAs. The mobile IP protocol provides IP routing service to public IP networks for mobile subscribers. The mobility management of WiMAX network supports two different MIP (mobile IP) protocols: client mobile IP (CMIP) and proxy mobile IP (PMIP). According to MIP protocols, in CMIP application, terminals can negotiate with network about packaging broadcast/multicast messages and use a reverse tunnel to send these messages to HA for processing.
A dynamic host configuration protocol proxy (DHCP Proxy) may be a functional entity of ASN-GW, providing DHCP proxy function for mobile IP terminals.
A dynamic host configuration protocol relay (DHCP Relay) may be a functional entity of ASN-GW, providing DHCP relay function for mobile IP terminals.
A domain name server (DNS) is deployed by operators, responsible for maintaining the binding relation between domain names and IP addresses.
Since the connection service network of WiMAX only provides the connection of IP layers, the service control function is not defined, and can't provide controllable telecommunication service, so it needs to be implemented with other mature networks. IMS is the first choice for network architecture of the next generation IP service and is the overall architecture of the future network, whose scheme architecture enhances the IP stream-based controllability and manageability, representing the development trend of the future network. Therefore, WiMAX access will constitute an important IP access network of IMS network, being able to supplement the limited bandwidth defect of other wireless access technologies.
The network architecture of the intercommunication between WiMAX network and IMS network is shown in FIG. 1. Call session control function (CSCF) is the core network element of IMS, and may be divided into proxy call session control function (P-CSCF), inquiry call session control function (I-CSCF), and service call session control function (S-CSCF). A home subscriber server (HSS) manages and processes subscriber's subscription data intensively in IMS system. P-CSCF is the first entrance point for the subscriber to access IMS network, and can select a subscriber home network. WiMAX subscribers are required to access P-CSCF through WiMAX network to access IMS network and enjoy IMS services.
Since P-CSCF is the first entrance point for the subscriber to access IMS network, the P-CSCF address needs to be obtained at first when the subscriber needs to access IMS through WiMAX system.
P-CSCF may be located in the home network, or in the visited network. In the prior art, there is no corresponding solution about how to obtain the address of P-CSCF of IMS network's access point, and how to determine whether the access point P-CSCF is located in the visited network or home network according to the related information when the subscriber roams.